Thermally developable light-sensitive elements

ABSTRACT

A photographic light-sensitive element capable of providing stable images by a thermal development, having a light-sensitive layer containing benzotriazolyl silver, a silver halide or an organic halide capable of forming a silver halide by the reaction with benzotriazolyl silver, a reducing agent, and an organic acid or a salt thereof.

United States Patent Ohkubo et a1.

[ 1 Feb.29,1972

[54] THERMALLY DEVELOPABLE LIGHT- SENSITIVE ELEMENTS [72] lnventors: Kinji Ohkubo; Takao Masuda; Junpel Noguchi, all of Kanagawa, Japan [73] Assignee: Fuji Photo Film Co., Ltd., Kanagawa,

v Japan [22] Filed: Feb. 21, 1967 [2]] Appl. No.: 617,498

[30] Foreign Application Priority Data Feb. 21, 1966 Japan ..41/l0383 [52] US. Cl ..96/67, 96/95, 96/114.1 [51] ..G03c l/76,G03c 1/06,G03c 1/02 [58] Field of Search ..96/94, 114.1, 95, 66 T, 76, 96/67; ll7/36.8, 36.9

[56] References Cited UNlTED STATES PATENTS 2,710,256 6/1955 Eckleretal....,..... 96/94 3,152,903 10/1964 Shepard et al ..96l95 3,152,904 10/1964 Sorensen et al.. .....96/76 3,218,168 11/1965 Workman ..96/67 3,392,020 7/1968 Yutzy et al ..96/67 3,457,075 7/1969 Morgan et a1 ,.96/67 OTHER PUBLICATIONS CA Abst. 1663b Vol. 65.

Primary ExaminerNorman G. Torchin Assistant Examiner-Mary F. Kelley AttorneySemmes & Semmes [5 7] ABSTRACT THERMALLY DEVELOPABLE LIGHT-SENSITIVE ELEMENTS BACKGROUND OF THE INVENTION For realizing an image by a dry developing method, various efforts have hitherto been made. One of them is an attempt in silver halide photography in which the development and fixing are conducting in one processing and such a process is called a monobath developing and fixing process. (E.g., cf. U.S. Pat. No. 2,875,048; British Pat. No. 954,453; and German Pat. No. 1,163,142). Another attempt is one in which the ,wet type processings in a conventional silver halide photography are conducted in a dry manner and is disclosed in, for example, German Pat. No. 1,174,159 and British Pat. Nos. 943,476 and 951,644. Still another attempt is one in which a silver salt compound other than silver halide is used and is disclosed in, for example, U.S. Pat. No. 3,152,904 and Belgian Pat. No. 663,112,

SUMMARY OF THE INVENTION The present invention relates to a light-sensitive element and more particularly to a light-sensitive element capable of forming images by heating.

In general, the light-sensitive element most widely used is a photographic light-sensitive element in which a silver halide is used, since such a photographic silver-halide light-sensitive element is excellent in sensitivity and gradation as compared with electrophotographic light-sensitive elements and other photographic light-sensitive elements. However, there are such difiiculties in such a photographic silver-halide light-sensitive element that the light-sensitive element must be subjected to several processings in order to prevent a thusly developed image from being blackened. The latter processings are generally called stopping, fixing" and stabilizing in a usual photographic method. Therefore, it is very desirable from the simplicity of processings to obtain an image by a dry developing method and to provide the permanent image while omitting fixing and other processes.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is concerned with a photographic light-sensitive element containing a combination of a light-insensitive and reducible organic silver salt and a slight amount of a light-sensitive silver salt, and more particularly a photographic light-sensitive element containing a benzotriazolyl silver and a slight amount of a silver halide.

Thus, an object of the present invention is to provide a novel photographic light-sensitive composition.

Another object of the present invention is to provide a novel image-reproducing method.

Still another object of the present invention is to provide a dry-type processing for conducting development by only heating without using any solutions in the developing process.

A further object of the present invention is to provide a light-sensitive element which can provide an image stable to light and capable of being stored almost substantially without subjecting the developed image to fixing and other processings.

Other objects and advantages of the present invention will become apparent by the following detailed descriptions.

Those objects can be achieved by using the thermally developable light-sensitive element of the present invention having a light-sensitive layer containing a combination of a light-insensitive and reducible organic silver salt and a slight amount of a light-sensitive silver salt such as a silver halide. That is, the thermally developable light-sensitive element according to the present invention comprises a support bearing at least one layer containing at least (a) a light-insensitive and reducible organic silver salt, (b) an inorganic halide capable of forming a light-sensitive silver halide by the reaction with the light-insensitive and reducible organic salt, (c) a reducing agent, and (d) at least one member selected from the group consisting of an organic acid or a salt thereof together with a suitable binder.

Asthe light-insensitive silver salt used in this invention,

there are illustrated silver salts of organic compounds having imino group such as a silver salt of benzotriazole or a silver salt of halogenor nitro-substituted benzotriazole; carbazolyl silver; and silver salt of saccharin (o-sulfobenzoic acid imide). Among them the silver salt of halogenor nitro-substituted benzotriazole is noninsensitive but the thermal development thereof is difficult. That is, the power of the silver salt to be reduced is weak. Carbazolyl silver is also difficult to be developed by heating. On the other hand, silver salt of saccharin can be developed thermally but the contrast between image and background is low, that is, the formation of heat fog is increased. However, a light-sensitive element containing silver salt of unsubstituted benzotriazole can be thermally developed and provide good contrast between image and background and hence this silver salt is most suitable for this invention.

Benzotriazolyl silver may be obtained by dissolving, for example, 59.5 g. of benzotriazole into 2 liters of methanol and adding into the solution 200 ml. of an aqueous solution of g. of silver nitrate with stirring at a normal temperature. After washing with water by decantation ten times, thus formed precipitate was separated by filtration, washed with water three times and dried.

Also, by conducting the reaction of benzotriazole and silver nitrate in a solution containing the below-mentioned binder, the size of the crystal grain may be controlled.

The organic halide capable of forming a silver halide by the reaction with the light-insensitive silver salt is a water-soluble or organic solvent-soluble compound shown by the general formula MXn wherein M represents hydrogen, ammonium or a metal such as strontium, cadmium, zinc, tin, chromium, sodium, potassium, barium, iron, cesium, lanthanum, copper, calcium, nickel, magnesium, aluminum, antimony, gold, cobalt, mercury, lead and beryllium; X represents a halogen such as chlorine, iodine and bromine, n represents the valency of metal, M. Among the above-mentioned inorganic halides, the iodide provides the silver salt thereof which is difficult to be printed out and hence is particularly preferable for the present invention.

Further, after dispersing in a binder solution the light-insensitive organic silver salt containing a slight amount of the silver halide, the dispersion may be subjected to a sulfur sensitization, a reduction sensitization or a noble metal sensitization, in the same manner as in conventional photographic light sensitive emulsion to increase the light-sensitivity.

As the reducing agent used in the present invention, there are illustrated aromatic monoor poly-hydroxy compounds and the derivatives thereof or aromatic monoor poly-amino compounds and the derivatives thereof. For example, a developer usually employed in a conventional photography may be used. They are, for example, hydroquinone, methylhydroquinone, chlorohydroquinone, bromohydroquinone, phenylhydroquinone, catechol, pyrogallol, hydroquinone monosulfonate, resorcinol, p-aminophenol, o-aminophenol, N-methyl-aminophenol y sulfate, 2-methoxy-4-aminophenol hydrochloride, 2,4-diaminophenol hydrochloride, sodium 1- amino-Z-naphthol-6-sulfonate, p-oxyphenyl glycine, 2-{3- hydroxyethyl-4-aminophenol, N,N-diethyl-p-phenylenediamine sulfite, l-naphthylamine-7-sulfonic acid (8 acid), M acid, l-hydroxy-4-methoxynaphthalene, l-hydroxy- 4-ethoxynaphthalene, 1,4-dihydroxynaphthalene, and lhydroxy-4-aminonaphthalene. These compounds may be used alone or amixture thereof. Moreover, other reducing agents such as 3-pyrazolidone, hydroxylamine hydrochloride, and reducing saccharines (glucose, lactose, etc.) may also be used in this invention. In any case, it is necessary for being used in thermal development that the oxidation reduction potential of the reducing agent at a normal temperature must be less than 500 m.v. (to standard hydrogen electrode).

As the organic acid used in this invention, there are such saturated aliphatic monocarboxylic acids having from nine to 26 carbon atoms as peralgonic acid, capric acid, lauric acid,

myristic acid, palmitic acid, stearic acid, arachic acid, behenic acid, cerotic acid, and the like. Among them, those having from 12 to 22 carbon atoms are particularly preferable. That is, the most preferable organic acids in this invention are lauric acid having 12 carbon atoms, myristic acid having 14 carbon atoms, palmitic acid having 16 carbon atoms, stearic acid having 18 carbon atoms, arachic acid having 20 carbon atoms and behenic acid having 22 carbon atoms. Furthermore, unsaturated aliphatic carboxylic acids such as linolic acid and oleic acid can be used in this invention. In this invention, further, aliphatic dicarboxylic acids having from 4 to 10 carbon atoms such as succinic acid, glutaric acid, adipic acid, sebacic acid, etc., may be used and among them sebacic acid is particularly preferable in the present invention since it has a good thermally developing property and provides a good contrast between image and background when used in photographic light-sensitive element. it is also odorless. Moreover, hydroxyl group substituted benzoic acids such as 2,3- dihydroxy benzoic acid, 2,4-dihydroxy benzoic acid, gentisic acid, 3 -resorcic acid, 7 -resorcic acid, protocathechuic acid, and gallic acid may also be employed in this invention in addition, the benzoic acid may have substituents such as a halogen atom and a methyl group. The salts such as alkali metal salts of the above-mentioned organic acids can also be effectively used in this invention. Since these organic compounds have their own reducing power, they can also be used as reducing agent and developing promoter simultaneously without the necessity of a reducing agent.

The proportions of the above-mentioned ingredients are generally determined by the reducing power, catalytic power, molecular weight and the like of the compounds to be used but generally it is preferable to use to one part by weight of the lighbsensitive and reducible silver salt (a), from 1/10 to l/ 100,000 part by weight of the light-sensitivity-providing material (b), from 1] 100 to 10 parts by weight of the reducing agent and l/ 100 to parts by weight of the organic acid (11) together with from l/ 10 to parts by weight of a suitable binder. Moreover, if necessary, the composition containing the above-mentioned ingredients may contain dye sensitizer, an oxide or a hydroxide of a metal, a hardening agent, a developing promotor, a matting agent, a wetting agent and the like.

A mixture of the above ingredients is applied to a sheetform support such as a pulp paper, a photographic paper, a baryta paper, a synthetic resin film, a metallic foil, a glass plate or the like. A part or the whole of these ingredients may be applied on the support in separate layers. Further, in order to coat these ingredients on a support uniformly and smoothly, it is preferable to use a suitable binder.

A transparent or translucent binder is desirable in this invention so as not to lower the transmission of light, and in particular photographic gelatin and solid high-molecular materials or resins are preferable. As the suitable high-molecular materials and resins there are illustrated polyvinylbutyral, cellulose acetate butyrate, polymethyl methacrylate, polyvinyl pyrrolidone, ethyl cellulose, polyethylene glycol, polystyrene, polyvinyl chloride, chlorinated rubber, polyisobutylene, a copolymer of butadiene and styrene, a copolymer of vinyl chloride and vinyl acetate, a copolymer of vinyl chloride, vinyl acetate and maleic acid, methcrylic resin, polyvinyl alcohol and the derivative thereof such as polyvinyl acetate.

Besides the above-mentioned materials, other additives for improving the contrast of image and background, which may be incorporated into the composition are oxides or hydroxides of metals such as zinc oxide, aluminum oxide, magnesium oxide, zinc hydroxide, aluminum hydroxide, cadmium hydroxide, magnesium hydroxide, and titanium oxide.

Further, the dye sensitizer, wetting agent, color toning agent, matting agent and hardening agent used in this invention may be oneconventionally employed in usual photographic silver halide light-sensitive elements.

The light-sensitive element having one or more light-sensi tive layers containing the above-mentioned composition is, after exposure to a tungsten lamp or an ultraviolet lamp,

heated by a suitable manner such as by passing through two heated rollers, placing it between two heated plates or by an infrared lamp, whereby the exposed part of the light-sensitive silver salt acts as a reducing catalyst by the actions of the reducing agent and the organic acid to reduce the light-inscm sitive silver salt and to provide an image.

The exposure time is considerably influenced by the kind of light sources, the developing conditions, the kinds of reducing agents and additives, and the sensitivity of the light-sensitive silver salt, but is in general from 0.001 second to 5 minutes.

The exposed light-sensitive element of this invention is usually developed by heating it to a temperature of above C., preferably l20-l 60 C. for 10 seconds.

The image thusly obtained by heating is not developed at a normal temperature and stable and permanent one.

As mentioned above, since the light-sensitive element of the present invention can be developed by a dry method after exposure and can provide a stable image without necessity of other processings, there are such advantages that the reproducing processing can be conducted rapidly and facilitated and the construction of processor is simplified.

Furthermore, there are other advantages: since any liquid chemicals for development and fixing are not used in the dry reproducing system, there are no dangers of contaminating hands and clothes, and copies can be obtained immediately in the dried state.

In the following examples the specific embodiments of this invention and the most preferable methods of preparing the thermally developable light-sensitive elements containing the The dispersion of the above composition in ethanol was applied to a photographic paper (per one square meter) and dried. After exposure to a tungsten lamp, this light-sensitive paper was heated to C. for 10 seconds to provide a good image in which the contrast between image and background was scarcely changed even if the thusly developed image were exposed to white light.

EXAMPLE 2 Cellulose acetatc-butyrate 5.6 g. Benzotriazolyl silver 2.8 g. Strontium iodide 0.07 g. sensitizing dye 0.001 g, Hydroquinone 0.84 g. Benmic acid 2l .0 g.

The dispersion of the above composition in acetone was applied to a photographic paper (per one square meter) and dried. After exposure to a tungsten lamp, the light-sensitive paper was heated to 1 10 C. for 10 seconds to provide a good image in which the contrast between image and background was scarcely changes when exposed to white light.

EXAMPLE 3 Polyvinylbutyral 4,8 g. Benzotriazclyl silver l.2 g. Cadmium iodide 0.05 g. sensitizing dye 0.00l g. Gallic acid 0.8 Laurie acid 6.0 g.

The dispersion of the above composition in ethanol was applied to a photographic paper (per one square meter) and dried. After exposure to a tungsten lamp, the'light-sensitive paper was heated to 140 C. for seconds to provide an image in which the contrast between image and background was not changed when exposed to white light.

EXAMPLE 4 Polyvinylbutyral 5.6 g. Benzotriazolyl silver 2.8 g Barium iodide 0.07 g sensitizing dye 0.001 g. Pyrogallol 0.05 g. Gallic acid 7.0 g.

The dispersion of the above composition in acetone was applied to a photographic paper (per one square meter) and dried. After being exposed to a tungsten lamp, the light-sensitive paper was heated to 160 C. for 5 seconds to provide a good image in which the contrast was scarcely changed when exposed to white light.

EXAMPLE 5 Polyvinylbutyral 4.0 g.

Benzotriazolyl silvcr 1.0 g. Ammonium bromide 0.05 g. sensitizing dye 0.001 g. l-Fhcnyl-S-pyrazolidone 0.05 g. Zinc oxide 1.0 g. Myristic acid 4.0 g.

The dispersion of the above composition in isopropyl a1- cohol was applied to a paper (per one square meter) and dried. After exposure to a tungsten lamp, the light-sensitive paper was heated to 160 C. for 5 minutes to provide a stable image having a good contrast.

EXAMPLE 6 Polyvinylbutyral 4.0 g. Strontium iodide 0.02 g. Sensitizing dye 0.0005 g. l-Hydroxy-4-methoxynaphthalene 0.1 g. Scbacic acid 4.0 g.

The above dispersion in ethanol was applied to a paper (per one square meter) and dried. Thereafter, the dispersion of the following composition in ethanol was applied to the formed layer:

Polyvinylhutyral 4.0 g. Benzotriazolyl silver 2.0 g. Monochlorohydroquinone 0.1 g.

followed by drying. After exposure to a tungsten lamp, the light-sensitive paper was heated to 150 C. for 10 seconds to provide a stable good image having a good contrast.

EXAMPLE 7 Polymethyl methacrylatc 4.0 g. Benzotrinzolyl silver 1.0 g. Sodium chloride 0.03 g. sensitizing dye 0.001 g. Hydroquinonc 0.3 g. Benzoic acid 5.0 g. 1,3-Diphenyl guanidine 1.0 g.

The dispersion of the above composition in ethanol was applied to a photographic paper (per one square meter) and dried. After exposure to a tungsten light, thus prepared lightsensitive paper was heated to 150 C. for 5 seconds to provide a stable image having a good contrast.

EXAMPLE 8 Polyvinylbutyral 4.0 g. Bcnzotriazolyl silver 1.0 3. Aluminum hydroxide 1.0 g. Scbacic acid 4.0 g.

The dispersion of the above composition in butyl alcohol was applied to a photographic paper (per one square meter). After drying, the ethanol solution of the following composition was applied to the above formed layer:

Polyvinylbutyral 0.3 g. Strontium iodide 0.05 g. l-Phcnyl-3-pyrazolidone 0.3 g. sensitizing dye 0.001 g.

followed by drying. After exposure to a tungsten light, the light-sensitive paper was heated to C. for 10 seconds to provide a stable image having a good contrast.

EXAMPLE 9 Gelatin 4.5 g. Benzotriazolyl silver 1.0 g. Strontium iodide 0.05 g. sensitizing dye 0.001 g. Hydroquinone 0.3 g. Sodium adipate 2.0 g.

The above composition was applied to a photographic paper (per one square meter) together with a suitable amount of color toning agent, a wetting agent and a hardening agent, and dried. After exposure to a tungsten lamp, the light-sensitive paper was heated to C. for 10 seconds to provide a stable image having a good contrast.

EXAMPLE 10 Into ml. of water was dried 18 g. of photographic gelatin and in the resulting solution was finely dispersed 3 g. of benzotriazolyl silver. The dispersion was heated to 60 C., mixed with 2 ml. of an aqueous solution of 5 percent potassium iodide, and the resulting solution was allowed to stand for 50 minutes at 60 C. and cooled to 40 C. Thereafter, the dispersion was mixed with the following composition:

sensitizing dye 0.0003 g. Sodium benzene sulfinate 1.8 g. Hydroquinone 0.9 g. Surface active agent 0.9 g. Sodium sebacate 12.0 g. 6% Formaldehyde solution 7.2 ml.

EXAMPLE 1 1 Into ml. of ethanol was dissolved 18 g. of polyvinylbutyral and in the solution 3 g. of benzotriazole silver was finely dispersed. The dispersion was heated to 50 C. and allowed to stand for 3 minutes and into the dispersion was added 2 ml. of an aqueous solution of 5 percent potassium iodide. After allowing to stand for 3 minutes, the thusly obtained dispersion was mixed with 0.5 ml. of an aqueous solution of 1 percent sodium nitrite and cooled to a normal temperature. The dispersion was then mixed with the following composition:

sensitizing dye 0.0003 g. Hydroquinone 0.9 g. Aluminum oxide 3.0 g. O-Toluylic acid 12.0 g.

and the resulting mixture was applied to a polyethylene terephthalate film (per one square meter) and dried. The amount of silver was 1.8 g./sq. m. as silver nitrate. After exposure to a tungsten lamp, thus obtained light-sensitive element was heated to 140 C. for seconds to provide a stable image. By adding 1 ml. of a 0.01 percent aqueous solution of sodium chloride aurate at the step of allowing to stand in the above procedure, the light-sensitivity was increased.

We claim:

1. A thermally developable light-sensitive element, comprising a support bearing thereon at least one layer, said layer containing one part, by weight, of benzotriazolyl silver; from 1/10 to 1/100,000 part, by weight, based on the weight of said benzotriazolyl silver, of an inorganic halide of the formula MX,,, wherein M is selected from the group consisting of hydrogen, amonium and a metal, and wherein X is a halogen, and wherein n is the valency of M; from 1/100 to l/10 part, by weight, based on the weight of said benzotriazolyl silver, of a reducing agent having an oxidation-reduction potential of less than 500 m.v., in comparison with the oxidation-reduction potential of a standard hydrogen electrode; and from 1/ 100 to 10 parts, by weight, based on the weight of said benzotriazolyl silver, of an organic acid and alkali metal salts thereof, said organic acid being selected from the group consisting of an aliphatic monocarboxylic acid having from 12 to 22 carbon atoms, an aliphatic dicarboxylic acid having from four to 10 carbon atoms, and substituted and unsubstituted benzoic acid, wherein said substituent is a member selected from the group consisting of a methyl radical, a halogen atom and a hydroxyl group.

2. The thermally developable light-sensitive element as in claim 1, wherein said reducing agent is a photographic developer.

4 3. The thermally developable light-sensitive element as in claim 1., wherein said aliphatic monocarboxylic acid is a member selected from the group consisting of lauric acid,

'myristic acid, palmitic acid, stearic acid, arachic acid and behenic acid.

4. The thermally developable light-sensitive element as in claim I, wherein said aliphatic dicarboxylic acid is a member selected from the group consisting of succinic acid, glutaric acid, adipic acid and sebacic acid.

5. The thermally developable light-sensitive element as in claim 1, wherein said substituted benzoic acid is a member selected from the group consisting of dihydroxybenzoic acid, toluic acid, dichlorobenzoic acid, and gallic acid.

6. A thermally developable light-sensitive element as in claim 1, wherein said alphatic monocarboxylic acid is palmitic acid.

7. A process for obtaining a print, comprising exposing the thermally developable light-sensitive element of claim 1 to the action of a tungsten or ultraviolet lamp for a period of time of from 0.001 to 5 minutes, and heating said element for a period of time of from 1 to 10 seconds at a temperature of from to C.

8. A thermally developablelight-sensitive element, comprising a support bearing thereon at least one layer, said layer containing one part, by weight, of benzotriazolyl silver, from 1/10 to 1/ 100,000 part, by weight, based on the weight of said benzotriazolyl silver, of an inorganic iodide of the formula Ml wherein M is selected from the group consisting of hydrogen, amonium and a metal, and wherein n 15 the valency of M; from H100 to l/ 10 part, by weight, based on the weight of said benzotriazolyl silver, of a reducing agent selected from the group consisting of photographic developers having an oxidation-reduction potential of less than 500 m.v., in comparison with the oxidation-reduction potential of a standard hydrogen electrode; and from 2.0 to 7.5 parts, by weight, based on the weight of said benzotriazolyl silver, of an organic acid and alkali metal salts thereof, said organic acid being selected from the group consisting of lauric acid, myristic acid, sebacic acid, and substituted and unsubstituted benzoic acid, wherein said substituent is a member selected from the group consisting of a methyl radical, a halogen atom and a hydroxyl group. 

2. The thermally developable light-sensitive element as in claim 1, wherein said reducing agent is a photographic developer.
 3. The thermally developable light-sensitive element as in claim 1, wherein said aliphatic monocarboxylic acid is a member selected from the group consisting of lauric acid, myristic acid, palmitic acid, stearic acid, arachic acid and behenic acid.
 4. The thermally developable light-sensitive element as in claim 1, wherein said aliphatic dicarboxylic acid is a member selected from the group consisting of succinic acid, glutaric acid, adipic acid and sebacic acid.
 5. The thermally developable light-sensitive element as in claim 1, wherein said substituted benzoic acid is a member selected from the group consisting of dihydroxybenzoic acid, toluic acid, dichlorobenzoic acid, and gallic acid.
 6. A thermally developable light-sensitive element as in claim 1, wherein said alphatic monocarboxylic acid is palmitic acid.
 7. A process for obtaining a print, comprising exposing the thermally developable light-sensitive element of claim 1 to the action of a tungsten or ultraviolet lamp for a period of time of from 0.001 to 5 minutes, and heating said element for a period of time of from 1 to 10 seconds at a temperature of from 120* to 160* C.
 8. A thermally developable light-sensitive element, comprising a support bearing thereon at least one layer, said layer containing one part, by weight, of benzotriazolyl silver, from 1/10 to 1/100,000 part, by weight, based on the weight of said benzotriazolyl silver, of an inorganic iodide of the formula MIn, wherein M is selected from the group consisting of hydrogen, amonium and a metal, and wherein n is the valency of M; from 1/100 to 1/10 paRt, by weight, based on the weight of said benzotriazolyl silver, of a reducing agent selected from the group consisting of photographic developers having an oxidation-reduction potential of less than 500 m.v., in comparison with the oxidation-reduction potential of a standard hydrogen electrode; and from 2.0 to 7.5 parts, by weight, based on the weight of said benzotriazolyl silver, of an organic acid and alkali metal salts thereof, said organic acid being selected from the group consisting of lauric acid, myristic acid, sebacic acid, and substituted and unsubstituted benzoic acid, wherein said substituent is a member selected from the group consisting of a methyl radical, a halogen atom and a hydroxyl group. 